Light emitting package

ABSTRACT

The present invention discloses a light emitting package, comprising: a base; a light emitting device on the base; an electrical circuit layer electrically connected to the light emitting device; a gold layer on the electrical circuit layer; a wire electrically connected between the light emitting device and the gold layer; a screen member having an opening and disposed on the base adjacent to the light emitting device; and a lens covering the light emitting device, wherein a bottom surface of the screen member is positioned higher than the light emitting device, and wherein an entire uppermost surface of the screen member is in contact with the lens.

This application is a Continuation of co-pending application Ser. No.13/182,393, filed on Jul. 13, 2011, that is a continuation ofapplication Ser. No. 13/036,947, filed on Feb. 28, 2011, now U.S. Pat.No. 8,003,997, that is a continuation of application Ser. No.12/860,792, filed on Aug. 20, 2010, now U.S. Pat. No. 7,977,684, that isa continuation of application Ser. No. 10/578,150, filed on May 3, 2006,now U.S. Pat. No. 7,821,020, which is a National Stage Entry ofPCT/KR05/02368 filed on Jul. 21, 2005, and which claims priority toApplication No. 10-2004-0107782 filed in the Korean Patent Office, onDec. 17, 2004. The entire contents of each of the applications arehereby incorporated by reference and for which priority and benefit areclaimed under 35 U.S.C. §119 and §120.

TECHNICAL FIELD

The present invention relates to a light emitting device package, andmore particularly, to a light emitting device package, which isexcellent in heat radiation performance and allows circuit design forcontrol of light emission of a semiconductor light emitting device to befreely done.

BACKGROUND ART

Generally, as a semiconductor light emitting device, a LED (LightEmitting Diode) can be included, which is a device used for convertingelectrical signals in the form of infrared, visible and ultravioletlight to emit light by using the characteristics of compoundsemiconductor.

As for the range of use of LEDs, LEDs are usually used for homeappliances, remote controllers, electric signs, displays, a variety ofautomation equipment, etc, and roughly divided into IRED (InfraredEmitting Diode) and VLED (Visible Light Emitting Diode). The structureof the above-said LED is as follows in general.

Generally, in a blue LED, a N type GaN layer is formed on a sapphiresubstrate, N-metal is formed on one side of the surface of the N typeGaN layer, and an active layer is formed on the portions except for theregion where the N-metal is formed. And, a P type GaN layer is formed onthe active layer, and P-metal is formed on the P type GaN layer. Theactive layer is a layer that generates light by holes flowing throughthe P-metal and electrons flowing through the N-metal being combined toeach other.

The aforementioned LED is used for home appliances, electric signs andthe like according to the intensity of light output. Especially, LEDshave a tendency to become slimmer as information communication equipmentare getting smaller in size, and peripheral equipment, such asresistors, condensers, noise filters, etc., are getting much smaller.

Consequently, light emitting devices are packaged in a surface mountdevice (hereinafter, “SMD”) type so that the light emitting device canbe directly mounted to a PCB (Printed Circuit Board). Accordingly, LEDlamps used as a display device are also being developed in a SMD type.

Such a SMD can substitute an existing simple lighting lamp, and used forlighting displays, character displays, image displays, etc. thatproduces variety of colors.

As above, as the range of use of LEDs has been becoming wider, arequired luminescence is becoming higher and higher, like in lamps usedfor daily life, rescue signaling lamps and the like. Thus, high outputLEDs have been widely used in recent years.

FIG. 1 is an explosive perspective view of a structure of a lightemitting device package according to the prior art.

As shown therein, in the structure of the light emitting device package100 according to the prior art, electrode lead frames 130 for applyingpower to a light emitting device from an external PCB are respectivelyformed and arranged on a package body 120.

A lens 110 is attached on top of the package body 120 in order toimprove the light efficiency of light generated from a LED 140 used asthe light emitting device.

An assembly having the LED 140 mounted therein is combined to the bottomof the package body 120. Firstly, a reflecting cup 160 with a high lightreflectivity is combined onto an electrical conductor 170. The LED 140is mounted on a sub mount 150 formed of silicon by flip chip bonding orwire bonding. Though not shown, a reflecting hole is formed inside thesub mount by etching the sub mount 150, a reflective layer is formed onthe reflecting hole, and then the LED 140 is mounted.

When the LED 140 is mounted on the sub mount 150, the sub mount 150 ismounted on the reflecting cup 160 formed on the conductor 170, and thenan electrical connection process with the electrode lead frames 130 ofthe LED body 120 is carried out so as to apply power.

The light emitting device package 100 thus assembled reflects the lightgenerated from the LED 140 against the reflecting cup 160, and thendiffuses the light to outside via the lens 110.

FIG. 2 is a view showing light emitting device packages 100 a, 100 b and100 c according to the prior art provided in plural number on a circuitsubstrate 200.

According to FIG. 2, unlike the light emitting device package presentedin FIG. 1, a plurality of LEDs 100 a, 100 b and 100 c are usedintegrally, in which they are provided in three colors of red, green andblue, respectively and lead frames 130 a, 130 b and 130 c arerespectively bonded onto the circuit substrate 200 by a solder 180.

However, the light emitting device package 100 having the aforementionedstructure has a problem that if the intensity of current is increased inorder to obtain light having a high output, a high temperature heat isgenerated due to poor heat radiation performance in the package. In acase where the high temperature heat exists in the package without beingradiated, the resistance becomes very high and thus the light efficiencybecomes deteriorated.

Further, the prior art light emitting device package 100 has a drawbackthat because the conductor 170, reflecting cup 160, package body 120 andthe like are separated from each other, the heat generated from the LEDis not easily transferred to outside due to a high heat resistance oftheir contact portions.

Further, there is an inconvenience that since only one LED is mounted inthe package body 120, three light emitting device packages must beplaced in a set in order to display high output white. In this case,there is another drawback that the control circuit becomes complex andthe volume becomes larger.

Further, in the plurality of single unit type light emitting devicepackages 100 a, 100 b and 100 c combined to each other, the surface areaof the entire substrate 200 is increased so as to connect electrodesfrom outside, thus increasing the cost of the assembling process.

Further, the structure of the prior art light emitting device package100 has a problem not only in terms of heat radiation but also in termsof structure. Specifically, there is a problem that colors cannot bemixed on an ideal point light source due to the characteristics of RGBcolor mixing since air bubbles may be formed upon molding and the singleunit type light emitting device packages are arranged on a wide surfacearea. Besides, there is a problem that the thickness of the lens to bemounted becomes larger due to the arrangement of an electrode,insulating layer, molding space and LED.

DISCLOSURE [Technical Problem]

The present invention is directed to solve the aforementioned problems,and it is an object of the present invention to provide a light emittingdevice package, which is improved in heat conductivity by eliminatingthe structure obstructing the heat radiation of a light emitting devicefrom a multilayered mounting structure when directly mounting the lightemitting device on a metal PCB.

Furthermore, it is another object of the present invention to provide alight emitting device package, in which each component of a lightemitting device is built in respective modules and mounted and aplurality of light emitting device packages are efficiently arranged ona metal PCB, and which makes circuit configuration easier, when directlymounting the light emitting device on the metal PCB.

Furthermore, it is yet another object of the present invention toprovide a light emitting device package, which improves a metal PCBstructure and a molding structure so as to minimize the thickness of alens in preparing a lens for the distribution of light and minimizes therejection rate caused by air bubbles generated during a molding process.

[Technical Solution]

To achieve the above objects, there is provided a light emitting devicepackage according to the present invention, comprising: a metal base; anelectrical circuit layer provided at an upper side of the metal base forproviding a conductive path; an insulating layer sandwiched between themeta base and the electrical circuit layer; a light emitting devicemounted on the top surface of the metal base in an open space from whichthe insulating layer is removed; an electrode layer provided at an upperside of the electrical circuit layer; and a connection portion forelectrically connecting the electrode layer and the light emittingdevice.

Additionally, there is provided a light emitting device packageaccording to another aspect of the present invention, comprising: ametal base; an electrical circuit layer provided at an upper side of themetal base for providing a conductive path; a light emitting devicemounted in a second region having a smaller thickness than a firstregion on the metal base; an insulating layer sandwiched between themeta base and the electrical circuit layer; an electrode layer providedat an upper side of the electric circuit layer; and a connection portionfor electrically connecting the electrode layer and the light emittingdevice.

ADVANTAGEOUS EFFECTS

According to the present invention, because heat generated from insidethe light emitting device package can be efficiently released, as manyhigh output light emitting devices as possible can be arranged invarious forms in a restricted space within the package. Thus, the lightemitting device package can be utilized in various ways for lightemitting device applications having a tendency to be decreased in size.

Additionally, according to the present invention, the manufacturing costcan be cut down, and the process can be minimized. Besides, excellentcharacteristics can be obtained uniformly in terms of heat radiation,optics with high light collectivity, mechanics, product reliability,etc.

DESCRIPTION OF DRAWINGS

The present invention will be more fully understood by reference to theaccompanying drawings, in which:

FIG. 1 is an explosive perspective view of a structure of a lightemitting device package according to the prior art;

FIG. 2 is a view showing light emitting device packages according to theprior art provided in plural number on a circuit substrate;

FIG. 3 is a cross sectional view of a light emitting device packageaccording to a first embodiment of the present invention;

FIG. 4 is a plan view of the light emitting device package according tothe first embodiment of the present invention;

FIG. 5 is a cross sectional view showing an internal structure of alight emitting device package according to a second embodiment of thepresent invention;

FIGS. 6, 7, 8 and 9 are views showing light emitting device packagesarranged on a single metal base in a straight line, a round, a squareand a hexagon; and

FIG. 10 is an enlarged view of the light emitting device packagesaccording to the embodiments of the present invention arranged in astraight line.

BEST MODE

Hereinafter, a light emitting device package according to preferredembodiments of the present invention will be described in detail withreference to the accompanying drawings.

First Embodiment

FIG. 3 is a cross sectional view of a light emitting device packageaccording to a first embodiment of the present invention

Referring to FIG. 3, the light emitting device package according to afirst embodiment of the present invention comprises a lens portion 310,a silk screen layer 392, a light emitting device 360, an electrode layer320, an electrical circuit layer 330, an insulating layer 340, and ametal base 350.

Firstly, the metal base 350 is the lowermost layer of a metal PCB, andfunctions to mount other components on its top layer and support them,and release heat generated from the light emitting device 360 toward thebottom surface. The metal base 350 can be combined to a heat sinkfurther provided on its bottom surface. It is preferable that the heatsink and the metal base 350 each form a fastening hole and are combinedto each other by screw type fastening.

Additionally, if a heat transfer material is applied or provided on thecombining surface between the metal base 350 and the heat sink, the heatradiation effect can be further maximized.

The insulating layer 340 electrically insulates between the electricalcircuit layer 330 and the metal base 350 so that currents flowing in theelectrical circuit layer 330 cannot flow toward the metal base 350.This, however, becomes an obstruction for an efficient heat radiationbecause the insulating layer 340 performs the function of insulationwhile simultaneously serving as a heat resistor.

Therefore, in the first embodiment of the present invention, theinsulating layer 340 is removed at least at the portion where the lightemitting device 360 is placed. That is, since the electrode structure ofthe light emitting device 360 is formed upward, it only needs to bephysically combined without help from the insulating layer 340.

In order for the surface where the light emitting device 360 is placedto be removed, the insulating layer 340 may be processed by milling oretching. And, the light emitting device 360 is combined by a bondingmember, such as a heat conductive hardening agent, when it is mounted onthe metal base 350.

The electrically circuit layer 330 is placed on the top of theinsulating layer 340. In the light emitting device package according tothe first embodiment of the present invention, since light emittingdevices 360 built in respective modules may be provided in pluralnumber, the electrical circuit layer 330 consists of a plurality ofcircuits for applying electricity to the light emitting devices 360.Like the insulating layer 340, the electrical circuit layer 330 isremoved at the portions where the light emitting devices 360 are placed.

As described above, since the light emitting devices 360 are provided inplurality numbers on one metal base 350, it is advantageous to constructthe electrical circuit layer 330 as a serially connected circuit on onemodule for the sake of circuit design or package application.

The electrode layer 320 for energizing the light emitting devices 360 ispositioned at the tip end of the electrical circuit layer 330, fromwhich the portions where the light emitting devices 360 are positionedare removed, and connected to a wire 390. Thus, in the first embodimentof the present invention, it can be known that the electrode layer 320serves as a prior art lead frame. The wire 390 performs the function ofelectrically connecting the light emitting devices and the electrodelayer.

Besides, the electrode layer 320 is generally made of metal, such asnickel, and a plating layer 322 is provided on the top surface thereofin order to improve the electric conductivity. Preferably, the platinglayer 322 is formed of gold at a thickness of 0.3 mm or more through anelectrolytic plating method. In such a structure, the electrical circuitlayer 330 and the electrode layer 320 whose top surface is plated arepreferably formed in a manner that the sum of the thickness of the twolayers is within 200 mm.

The light emitting device 360 is provided with a light emitting portionmade of a compound semiconductor and an electrode for applying current,and when a power is applied from the electrode layer 320, light emissionis performed. As the light emitting device, a light emitting diode ispreferably exemplified.

As made clear by the aforementioned structure, the light emitting device360 can be directly mounted on the metal base 350 by being embedded inan opening space A of the insulating layer 340, electrical circuit layer330 and electrode layer 320.

As the light emitting device 360, can be included a SiOB (SiliconOptical Bench) chip, a red LED chip, a green LED chip, a blue LED chip,a yellow LED chip, an orange LED chip, etc. Especially, the SiOB chipdenotes a chip that is made by etching a cup-shaped space into a siliconsubstrate and mounting a LED in the space. The silicon substrate may bemade of other material.

The electrode layer 320 has a silk screen layer 392 formed at an outerside of the portion to be bonded by the electrode of the light emittingdevice 360 and the wire 390. The lens portion 310 is attached to thesilk screen layer 392. The lens portion 310 can be provided by a moldingportion 380 where a transparent resin material is to be molded, and themolding portion 380 can be molded at a precise position by a procedureof attaching to the silk screen layer 392.

FIG. 4 is a plan view of the light emitting device package according tothe first embodiment of the present invention, especially, in which theshape of the silk screen layer is clearly illustrated. But, the wire isvery small and thus not shown, and it is needless to say that aplurality of chips can be mounted simultaneously on the light emittingdevice 360.

Referring to FIG. 4, to protect the light emitting device 360 and thewire 390, the internal space of the molding space 380 constituting thelens portion 310 is molded from the upper surface of the metal base 350at a height larger than that of the portion where the wire 390 isplaced, especially, it is molded using a synthetic resin material suchas epoxy or silicon. The molding portion 380 is a kind of highrefractive filler material, and uniformly distributes the light diffusedby the light emitting device 360.

As seen from above, the light emitting device package according to thefirst embodiment of the present invention has a merit that it is reducedin size, is freely arranged and can be built in respective modules withthe improvement of heat radiation effect since a reflecting cup, a leadframe and a lens portion of the prior art light emitting device packageare integrated and mounted on a metal PCB.

Second Embodiment

In explaining the second embodiment of the present invention, many partsof the foregoing description of the first embodiment of the presentinvention are incorporated. Hereinafter, only characteristicallydifferent portions will be described in detail.

FIG. 5 is a cross sectional view showing an internal structure of alight emitting device package according to a second embodiment of thepresent invention.

Referring to FIG. 5, the light emitting device package according to asecond embodiment of the present invention comprises a lens portion 310a, a silk screen layer 392 a, a light emitting device 360 a, anelectrode layer 320 a, an electrical circuit layer 330 a, an insulatinglayer 340 a, a wire 390 a and a metal base 350. The functions, structureand material of the lens portion 310 a, silk screen layer 392 a, lightemitting device 360 a, electrode layer 320 a, electrical circuit layer330 a and insulating layer 340 a are similar to those of the firstembodiment of the present invention.

The only difference from the first embodiment is that only parts of themetal base 350 a are removed in the region where the light emittingdevice 360 a is placed, and the light emitting device 360 a is placed ina removal region B from which the metal base 350 a is removed.

More specifically, the removal region B can be processed by a givenprocessing method such as milling or the like. As the light emittingdevice 360 a is embedded in the removal region B, the top surface of thelens portion 310 a establishes equilibrium, and the overall height ofthe lens portion can become smaller than in the first embodiment.Besides, the light emitting device 360 a is inserted into the removalregion B, thus allowing the bottom surface to be attached by a thermalconductive hardening agent.

The light emitting device 360 a mounted in the removal region B isenergized by the electrode layer 320 a and the wire 390 a positionedrelatively higher than the light emitting device 360. Like in the firstembodiment of the present invention, a molding portion 380 a is providedin order to protect the light emitting device 360 a and the wire 390 a.

At this time, the molding portion 380 is also relatively low in height,which is possible because the light emitting device 360 a is insertedand placed in the metal base 350 a, and the space for bonding the wire390 a is also placed at a relatively lower side. In the secondembodiment of the present invention, it is preferable that the moldingportion 380 a is formed at such a height as to protect the lightemitting device 360 a and the bonding portion 390 a.

By such a structure, the thickness of the lens portion 310 can besmaller, and furthermore the highest side of the lens portion 310 a canbe planarized and reduced in height, thus enabling it to use variouskinds of lenses including a Fresnel lens.

Moreover, a molding member of a synthetic resin material such as epoxyor silicon is directly injected into the recess of the metal base 350 a,and thus there is no need to use a gap for injecting the molding memberas in the prior art. By this, air bubbles can be prevented fromgeneration upon molding.

As explained above, the position of the light emitting device 360 a, thestructure of the molding portion 380 a and a decrease of the lensthickness allows red, green and blue to be mixed with each other on muchsmaller regions, thereby making a finally diffused light come close to apoint source of light.

Moreover, the removal region B may be formed in a cylindrical recess, orthe sides of the cylindrical recess B may be formed inclined at apredetermined angle. The inner surface of the recess B forming thepredetermined angle can increase the reflection efficiency of light.Furthermore, it is preferable that the sides of the recess B are glosscoated or provided with a reflection material so as to improve thereflectivity. Namely, in a case where the light emitting device 360 alight emits within the cylindrical recess B, the inclined surface of themetal base 350 a reflects almost all of the light upward, and thus thelight emission efficiency of the light emitting device 360 can beincreased.

Third Embodiment

The third embodiment of the present invention is characterized in thatit proposes an overall structure in which the light emitting packageproposed in the first and second embodiments is used as a single unit.

Referring to FIG. 6, according to this embodiment, a plurality of lightemitting device packages are provided on one metal base 350 a, and lensportions 310 a are respectively arranged on the light emitting devicepackages. Of course, it is possible to mount high output light emittingdevice packages in a smaller space by the electrical circuit layer 330 ahaving a circuit for connecting the respective light emitting devicepackages. In the drawing, it is shown that the light emitting devicepackages are arranged in a straight line. That is, a plurality of lightemitting device modules provided by the respective light emittingdevices is arranged in a straight line.

In this case, in the first and second embodiments of the presentinvention, the metal PCB may have a reflection material on the surfaceof the layer open to the top surface out of the electrical circuitlayers 330 and 330 a, electrode layers 320 and 320 a, insulating layers340 and 340 a and metal bases 350 and 350 a, or may be gloss coated. Bythe reflection material or gloss-coating, the light emitted from thelight emitting devices 360 and 360 a provided in plural number have ahigh reflection efficiency even on the metal PCB outside the lensportions 310 and 310 a.

Moreover, in the drawing, the portions indicated in round exemplify theshape of a Fresnel lens serving as the lens portion 310 a, and themounting surface is indicated in a simplified form by the metal base 350a.

FIGS. 7, 8 and 9 show another embodiments in which light emitting devicepackages on a single metal base 350 a can be arranged in a round shape,a square shape and a hexagonal shape, respectively. These arrangementsof the light emitting device packages may change according to specificuses for applying light emitting devices.

FIG. 10 is an enlarged view of the light emitting device packagesaccording to the embodiments of the present invention arranged in astraight line.

Referring to FIG. 10, in the electrical circuit layer 330 a, it can beseen that the respective light emitting device packages indicated as thesilk screen layer 392 a on the insulating layer 340 a are supplied withpower so that the plurality of light emitting device packages may beenergized simultaneously through a serial connection circuit. Of course,it is also possible to supply power to the respective light emittingdevices of green, red and blue by providing a plurality of serialconnection circuits.

Meanwhile, a fastening hole C of the metal base 350 a is a hole forcombining via a heat sink and a screw type fastening structure in a casewhere an additional heat sink is secondarily provided on the metal base350 a as explained in the first embodiment of the present invention.

MODE FOR INVENTION

The light emitting device package according to the present inventionproposes a configuration for emitting a high output light, and isprimarily focused on an arrangement structure of light emitting devices.To achieve the aforementioned objects, the present invention may bepracticed in a variety of embodiments without departing from theforegoing embodiments, and such embodiments may be construed as withinthe spirit and scope of the present invention.

INDUSTRIAL APPLICABILITY

According to the light emitting package of the present invention,because heat generated from inside the light emitting device package canbe efficiently released, as many high output light emitting devices aspossible can be arranged in various forms in a restricted space, andthus, the light emitting device package can be utilized in various waysfor products with a tendency to be decreased in size.

Additionally, according to the present invention, the manufacturing costcan be cut down, and the process can be minimized since light emittingdevice packages built in respective modules can be integrated andmounted through a structural improvement without having a radiator.

Besides, according to the present invention, it is possible to obtain alight emitting device package having excellent characteristics uniformlyin terms of heat radiation, optics with high light collectivity,mechanics, product reliability, etc.

1. A light emitting package, comprising: a base; a light emitting deviceon the base; an electrical circuit layer electrically connected to thelight emitting device; a gold layer on the electrical circuit layer; awire electrically connected between the light emitting device and thegold layer; a screen member having an opening and disposed on the baseadjacent to the light emitting device; and a lens covering the lightemitting device, wherein a bottom surface of the screen member ispositioned higher than the light emitting device, and wherein an entireuppermost surface of the screen member is in contact with the lens. 2.The light emitting package of claim 1, wherein an edge portion of thelens is in contact with the screen member.
 3. The light emitting packageof claim 1, further comprising an electrode layer disposed on theelectrical circuit layer, wherein the gold layer is plated on the topsurface of the electrode layer.
 4. The light emitting package of claim3, wherein the electrode layer comprises nickel.
 5. The light emittingpackage of claim 1, further comprising an insulating layer between theelectrical circuit layer and the base.
 6. The light emitting package ofclaim 1, wherein the lens is formed with a resin material guided by thescreen member.
 7. The light emitting package of claim 1, furthercomprising a heat sink combined with the base.
 8. The light emittingpackage of claim 1, wherein the base is formed of a metal.
 9. A lightemitting unit, comprising: at least one light emitting package, eachincluding: a base, a light emitting device on the base, an electricalcircuit layer electrically connected to the light emitting device, agold layer on the electrical circuit layer, a wire electricallyconnected between the light emitting device and the gold layer, a screenmember having an opening and disposed on the base adjacent to the lightemitting device, and a lens covering the light emitting device, whereina bottom surface of the screen member is positioned higher than thelight emitting device, and wherein an entire uppermost surface of thescreen member is in contact with the lens.
 10. The light emitting unitof claim 9, further comprising a heat sink combined with the base. 11.The light emitting unit of claim 9, wherein the base is formed of ametal.
 12. A light emitting package, comprising: a base; a lightemitting device on the base; an electrical circuit layer electricallyconnected to the light emitting device; a screen member having anopening and disposed on the base adjacent to the light emitting device;and a lens covering the light emitting device, wherein a cross-sectionalshape of the screen member is substantially rectangular, and a width ofthe cross-sectional shape of the screen member being larger than aheight of the cross sectional shape of the screen member, wherein ashape of the opening of the screen member is substantially circular, andwherein an edge of the lens is in contact with the screen member. 13.The light emitting package of claim 12, further comprising an electrodelayer disposed on the electrical circuit layer.
 14. The light emittingpackage of claim 12, further comprising an insulating layer between theelectrical circuit layer and the base.
 15. The light emitting package ofclaim 12, wherein the lens is formed with a resin material guided by thescreen member.
 16. The light emitting package of claim 12, furthercomprising a heat sink combined with the base.
 17. The light emittingpackage of claim 12, wherein the screen member is formed in a layer. 18.The light emitting package of claim 12, wherein the base is formed of ametal.
 19. A light emitting unit, comprising: at least one lightemitting package, each including: a base, a light emitting device on thebase, an electrical circuit layer electrically connected to the lightemitting device, a screen member having an opening and disposed on thebase adjacent to the light emitting device, and a lens covering thelight emitting device, wherein a cross-sectional shape of the screenmember is substantially rectangular, and a width of the cross-sectionalshape of the screen member being larger than a height of the crosssectional shape of the screen member, wherein a shape of the opening ofthe screen member is substantially circular, and wherein an edge of thelens is in contact with the screen member.
 20. The light emitting unitof claim 19, further comprising a heat sink combined with the base. 21.The light emitting unit of claim 19, wherein the screen member is aformed in a layer.
 22. The light emitting unit of claim 19, wherein thebase is formed of a metal.